Flame detector



L. B. WAGNER v FLAME DETECTOR Oct. 16, 1962 l 2 Sheets-Sheet l FiledASep.. 17, 1959 INVENTOR. fz/W0 WHG/YER.

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Uct. 16, 1962 1 B. WAGNER 3,059,080

4 FLAME DETECTOR Filed Sept. 17, 1959 2 Sheets-Sheet 2 Pn. 4|.- Plq. 'a-

INVENTOR. 5L/wp E, WHG/mv.

3,059,080 FLAME DETECTOR Leland B. Wagner, Goshen, Ind., assignor to Penn Controls, Inc., Goshen, ind., a corporation of Indiana Filed Sept. 17, 1959, Ser. No. 840,666 Claims. (Cl. 2011-138) This invention relates generally to combustion responsive devices and in particular to a flame detector adapted for mounting within lche blast tube of a conventional oil burner.

In conventional oil burner installations the combustion responsive switch, lforming a part o-f the control for the burner, is mounted at a location in the burner stack where it can properly indicate the presence or absence of combustion. Since this location is relatively remote from the burner llame itself, and because of the thermal inertia ofthe oil red furnaces heat exchange surfaces and stack, the reaction time of such remotely mounted combustion responsive switches is prolonged. Further, since the combustion responsive switch is mounted separately from the burner at a location dictated by the particular installation, this control cannot be pre-wired by the burner manufacturer.

The apparatus herein disclosed and claimed represents an improved version of the flame detector disclosed and claimed in my United States Patent 3,033,978, issued .lune 12, 1962 and titled Flame Detector.

It is an object of the present invention to provide a flame detector switching device adapted Vfor mounting within the blast tube of an oil burner to directly view the burner llame and which utilizes the reflector member for directing heat to the bimetal temperature responsive element.

A further object of the present invention is to provide a ame detector switching device of the type referred to which is sealed against the entry of soot or dirt but which retains a relatively high degree of sensitivity to the presence or absence 'of a burner flame.

Another object is to provide a llame detector wherein a bimetal element has the transfer of heat to it by conduction minimized and the transfer of heat to it by radiation maximized.

An additional object is to provide a flame detector wherein a bimetal element has the transfer of heat by conduction from it to surrounding objects minimized.

Still another object is to provide a bimetal element in a flame detector which is supported by a mounting which has a low thermal conductivity and has a minimum area in contact with the bimetal element.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

FIG. l is an end View of an assembly embodying the present invention.

FIG. 2 is a side elevational view of a switch accommodating :cartridge of the assembly surrounded by a sectional view of its housing taken along the line 2 2 of FIG. l.

FIG. 3 is an end 4View of the assembly taken from the end opposite that of FIG. l.

FIG. 4 is a sectional view of a portion of the assembly taken along the line 2 2 of FIGURE 1.

FIG. 5 is a front view of the reflector plate.

FIG. 6 is an end elevational view of a stainless steel cup-shaped element used to enclose the opposite end of the assembly.

FIG. 7 is an end View of the attachment `for clam-ping the assembly to the nozzle of an oil burner..

Referring initially to FIGS. 1 and 7, the flame detecting apparatus includes a cylindrical housing 10 having States arent 3,059,080 Patented Oct. 16, 1962 ice welded thereto a sidewardly extending, threaded member 11. Tihe threaded member is adapted to receive a nut (not shown) an-d is inserted into a slot 12 in a bracket 13 which is spot welded to a ring clamp 14 as may be seen in FIG. 7. The clamp 14 is adapted to encircle the nozzle of an oil `burner within the oil burner blast tube, the nozzle being shown schematically at 16 in FIG. 7. rlightening of the bolt 18 serves to clamp the ring 14 about the oil burner nozzle and provides a mounting means for the llame detector. By means of the elongated slot 12, the flame detector may be varied in position along the axis of the oil burner nozzle.

rihe housing l() is cup-shaped and its closed end 15, disposed remotely from the burner llame, is provided with three apertures bounded by outwardly extending flanges 19. The apertures are filled with a fusible material such as glass indicated at 2l in FIG. 2, the fusible material supporting terminal lugs 22. Slidably inserted within the housing is a switch accommodating cartridge which includes a frame 23. Rearwardly extending tabs 24, formed integrally with the frame, are bent to secure the frame to an end plate 26 formed of electrical insulating material. Extending from the rear face of the end plate 26 are resilient contact leaves 27 which engage the inner ends of the terminals 22 and make electrical contact therewith. One of the leaves 27 is electrically connected to the plate 28, another is connected to a switch contact 29 and the third is connected to a bracket 31 'carrying a second switch contact 32. A movable contact structure cooperates with the contacts 29 and 32 by means of a slip-friction arrangement which is described in detail an-d claimed in my above-mentioned copending application.

In general, the movable contact structure includes a plate 33 which extends between the contacts 29 and 32 and is carried by a bracket 34. The bracket 34 is apertured to freely receive the thrust element 36. The bracket carries a leaf-type spring 37 whose free end frictionally engages the thrust member 36. A screw 38 threaded into the plate 28 serves to electrically attach one end of a pig-tail lead wire 39 to the bracket '34.

The open end of the cartridge provided by the frame 23 is closed by a reiiector plate 41, the reflector plate butting against the marginal edge of the frame 23 as may be seen in FIG. 4. As may best be seen in FIG. 4, two yannular members 42, which may -be formed of Teflon or similar material abut the plate 41 and have formed therein diametrically opposed notches y43 which have inclined sidewalls. The adjacent notches in the members 42 thus provide substantially V-shaped depressions. Seated in the depressions are the ends of a bimetal element 44 which extends diametrically across the housing. Extending from the inner face of the element 44 and freely through an aperture 46 in the reflector plate 41 is the -thrust member '36, the thrust member being Welded to the bimetal element. An annular hold-down ring 47 overlies the outermost one of the annular members 42 and the assembly thereby formed is held in stacked relation by means of forwardly exten-ding tabs 48 which are formed integrally with the frame '23.

'In assembling the apparatus the cartridge subassembly is inserted in the housing 10 and positioned so that the leaves 27 engage the terminals 22. The end of the housing is then sealed by means of a stainless steel cup-shaped element 49. The element 49 is provided with a black, non-reflecting finish on its outer face so as to absorb radiant heat from the burner flame. The edge of the sealing plate 49 is welded to the adjacent annular, marginal surface of the housing 10. As may best be seen in FIG. 6, the plate 49 is provided with four diametrically opposed raised portions 51 which accommodate the tabs 48. Stiffening ribs 52 extend between the raised por- 3,059, oso

tions 51 and provide the required rigidity for the relatively thin plate 49.

In operati-on, with the assembly clamped upon the nozzle of an oil burner, the plate or element 49 will be facing the burner llame and will receive radiant heat therefrom. In turn, the bimetal element 44 will receive heat both by radiation `and convection from the inner face of the sealing plate 49. The resulting movement of the bimetal member in response to the presence or absence or llame at the burner will serve to position the contact plate 313 against one or the other of the fixed contacts 29 and 32. Because of the slip-friction connection between the thrust member 36 and the bracket 34, the contacts will be operated upon a predetermined change in temperature as is Well known in the art. The operation Iof the switching elements is not described in detail herein but is described `in detail in my copending application.

While the bimetal element 44 is sealed from direct thermal radiation from the burner ame by the plate 49, the sensitivity of response of the flame detector is maintained at the desired point because of the presence of the rellector plate 41. As may Ibe seen in FIGS. 4 and 5, the reflector plate is of concavo-convex configuration, and its concave surface 41a is provided with a smooth, heat reflecting finish. The reector plate serves to focas heat radiated from the inner face of the sealing plate 49 on to the bimetal element 44, and the curvature of the plate tends to retain a pocket of heated air about the bimetal element. The ame detector assembly just described provides a structure which is sealed against entry of soot or dirt into the switching elements. While the bimetal element 44 is `shielded from direct radiation from the burner iiame, the concave-convex reflector plate 41 serves to maintain the sensitivity and rapidity of response of the device.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

The invention claimed is:

1. A heat detector control device comprising a housing, a portion of said housing facing a source of heat being constructed of a thin metallic wall with a non-reflective outer surface, a reflector mounted in said housing, mounting means constructed at least in part of a nonmetallic material having a low thermal conductivity, a bimetal element mounted in said housing and in contact with only the non-metallic part of said mounting means to operate a control means as said bimetal element expands and contracts, said reflector being positioned to receive radiant heat energy from said portion of said housing and to focus said heat energy onto said bimetal element.

2. A radiant heat detecting switching device adapted to receive radiant heat from a source thereof, said device comprising a tubular housing having two closed ends with one said end facing the heat source being constructed of a thin metallic wall with a dull black outer surface, spaced stationary switch contacts supported within said housing, mounts constructed of a material having a low thermal conductivity in said housing, a temperature responsive Ibimetal element mounted diametrically across the said tube near said one end facing the heat source by said mounts, a thrust member extending into said housing from the inner face of said bimetal element and adapted to be moved lineally as said element responds to temperature change, a clutch arm slidably mounted on said thrust member, resilient means acting between said thrust member and said arm to resist movement of said arm along said member, a contact element carried by said arm and adapted to engage one or the other of said stationary contacts depending upon the direction of motion of said thrust member, and a reflector mounted in said tubular housing to receive radiant heat energy from said one end facing the heat source and to focus said heat energy onto said bimetal element.

3. A sensitive heat detector comprising a heat responsive element, a mounting composed at least in part of a non-metallic material having a low thermal conductivity and supporting said element with only a small area of the non-metallic part in contact with said element to minimize the transfer of heat by conduction between said element .and `any surrounding objects, and a means for concentrating infrared radiation onto said element to maX- imize the transfer of heat by radiation to said element.

4. A lsensitive heat detector comprising a bimetal element, a mounting composed at least in part of a nonmetallic material having a low thermal conductivity and supporting said bimetal element with only a small area of the non-metallic part in contact with the edges of said element to minimize the transfer of heat by conduction between said element and any surrounding objects, and a reflector for concentrating infrared radiation onto said element `to maximize the transfer of heat by radiation to said element.

5. A sensitive heat detector in accordance with claim 4 wherein said bimetal element is an elongated thin bimetal strip and the non-metallic part of said mounting has V- shaped notches receiving the ends of said element to establish a minimum contact area between said mounting and said element.

References Cited in the le of this patent UNITED STATES PATENTS 726,490 Yerrington Apr. 28, 1903 1,426,447 Apfel Aug. 22, 1922 1,997,598 Pendleton Apr. 16, 1935 2,162,098 McCabe June 13, 1939 2,555,273 Koci May 29, 1951 2,824,194 Moorhead Feb. 18, 1958 2,914,647 Ganske et al. Nov. 24, 1959 

